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RE: [PWE3] Last Call: <draft-ietf-pwe3-redundancy-bit-06.txt> (Pseudowire Preferential Forwarding Status Bit) to Proposed Standard



Dear all,
I received comments from Daniel regarding the intended use of the optional active PW selection mechanism in section 5.1. I pasted below the corresponding paragraph of Section 5.1 with the changes we agreed to underlined. 
 
He also asked if the default active PW selection mechanism should be referenced in Section 5.2 with the Master/Slave mode of operation. Although, it is not stricly required for interoperability, implementations would benefit from a consistent behaviour. I used SHOULD in that case. The text is also pasted below with the changes underlined.
 
Let me know if you have any comments on this.
 
Regards,
Mustapha.
 
=======================================================================================
I. Changes to Section 5.1 - 3rd paragraph:
"

If more than one PW qualifies for the Active state, each PW endpoint MUST implement a common mechanism to choose the PW for forwarding. The default mechanism MUST be supported by all implementations and operates as follows:

1.     For FEC128 PW, the PW with the lowest pw-id value is selected.

2.     For FEC129 PW, each PW in a redundant set is uniquely identified at each PE using the following triplet: AGI::SAII::TAII. The unsigned integer form of the concatenated word can be used in the comparison. However, the SAII and TAII values as seen on a PE node are the mirror values of what the peer PE node sees. To have both PE nodes compare the same value we propose that the PE with the lowest system IP address use the unsigned integer form of AGI::SAII::TAII while the PE with the highest system IP address use the unsigned integer form of AGI::TAII::SAII. This way, both PEs will compare the same values. The PW which corresponds to the minimum of the compared values across all PWs in the redundant is selected.

Note 1: in the case where the system IP address is not known, it is recommended to implement the optional active PW selection mechanism described next.

Note 2: in the case of segmented PW, the operator needs to make sure that the pw-id or AGI::SAII::TAII of the redundant PWs within the first and last segment are ordered consistently such that the same end-to-end MS-PW gets selected. Otherwise, it is recommended to implement the optional active PW selection mechanism described next.

The PW endpoints MAY also implement the following optional active PW selection mechanism.

1.     If the PW endpoint is configured with the precedence parameter on each PW in the redundant set, it must select the PW with the lowest configured precedence value.

2.     If the PW endpoint is configured with one PW as primary and one or more PWs as secondary, it must select the primary PW in preference to all secondary PWs. If a primary PW is not available, it must use the secondary PW with the lowest precedence value. If the primary PW becomes available, a PW endpoint must revert to it immediately or after the expiration of a configurable delay.

3.     This active PW selection mechanism assumes the precedence parameter values are configured consistently at both PW endpoints and that unique values are assigned to the PWs in the same redundancy set to achieve tie-breaking using this mechanism.

"
 
II. Changes to Section 5.2 - 5th paragraph:
"

If more than one PW qualify for the Active state, the Master PW endpoint node selects one. There is no requirement to specify a default active PW selection mechanism in this case but for consistency across implementations, the Master PW endpoint SHOULD implement the default active PW selection mechanism described in Section 5.1.

If the Master PW endpoint implements the optional active PW selection mechanism based on primay/secondary and precedence parameters, it MUST follow the following behaviour:

1.     If the PW endpoint is configured with the precedence parameter on each PW in the redundant set, it must select the PW with the lowest configured precedence value.

2.     If the PW endpoint is configured with one PW as primary and one or more PWs as secondary, it must select the primary PW in preference to all secondary PWs. If a primary PW is not available, it must use the secondary PW with the lowest precedence value. If the primary PW becomes available, a PW endpoint must revert to it immediately or after the expiration of a configurable delay.

"
=======================================================================================


From: Aissaoui, Mustapha (Mustapha)
Sent: Wednesday, March 07, 2012 12:56 PM
To: Andrew G. Malis
Cc: stbryant@xxxxxxxxx; draft-ietf-pwe3-redundancy-bit@xxxxxxxxxxxxxx; pwe3@xxxxxxxx; ietf@xxxxxxxx
Subject: RE: [PWE3] Last Call: <draft-ietf-pwe3-redundancy-bit-06.txt> (Pseudowire Preferential Forwarding Status Bit) to Proposed Standard

makes sense Andy.
 
Thanks,
Mustapha.


From: Andrew G. Malis [mailto:amalis@xxxxxxxxx]
Sent: Wednesday, March 07, 2012 12:53 PM
To: Aissaoui, Mustapha (Mustapha)
Cc: stbryant@xxxxxxxxx; draft-ietf-pwe3-redundancy-bit@xxxxxxxxxxxxxx; pwe3@xxxxxxxx; ietf@xxxxxxxx
Subject: Re: [PWE3] Last Call: <draft-ietf-pwe3-redundancy-bit-06.txt> (Pseudowire Preferential Forwarding Status Bit) to Proposed Standard

Mustapha,

You might want to wait for any other LC comments before updating.

Thanks,
Andy

On Wed, Mar 7, 2012 at 9:49 AM, Aissaoui, Mustapha (Mustapha) <mustapha.aissaoui@xxxxxxxxxxxxxxxxxx> wrote:
Ooops. Thank you for pointing this out Stewart. I will make the update and publish a new revision.

Mustapha.

-----Original Message-----
From: Stewart Bryant [mailto:stbryant@xxxxxxxxx]
Sent: Wednesday, March 07, 2012 12:48 PM
To: draft-ietf-pwe3-redundancy-bit@xxxxxxxxxxxxxx
Cc: ietf@xxxxxxxx; pwe3@xxxxxxxx
Subject: Re: Last Call: <draft-ietf-pwe3-redundancy-bit-06.txt> (Pseudowire Preferential Forwarding Status Bit) to Proposed Standard


Authors

There was on point that I notice that you did not address from the AD review and so I am picking it up as a LC comment:

In section 10 you say:

   "This document makes the following update to the PwOperStatusTC
   textual convention in RFC5542 [8]: "

This update should be recorded in the metadata (top left front page) and it is usual to put a one line note in the abstract.

Stewart



On 07/03/2012 17:00, The IESG wrote:
> The IESG has received a request from the Pseudowire Emulation Edge to
> Edge WG (pwe3) to consider the following document:
> - 'Pseudowire Preferential Forwarding Status Bit'
>    <draft-ietf-pwe3-redundancy-bit-06.txt>  as a Proposed Standard
>
> The IESG plans to make a decision in the next few weeks, and solicits
> final comments on this action. Please send substantive comments to the
> ietf@xxxxxxxx mailing lists by 2012-03-21. Exceptionally, comments may
> be sent to iesg@xxxxxxxx instead. In either case, please retain the
> beginning of the Subject line to allow automated sorting.
>
> Abstract
>
>
>     This document describes a mechanism for standby status signaling of
>     redundant pseudowires (PWs) between their termination points. A set
>     of redundant PWs is configured between provider edge (PE) nodes in
>     single-segment pseudowire (SS-PW) applications, or between
>     terminating provider edge (T-PE) nodes in multi-segment pseudowire
>     (MS-PW) applications.
>
>     In order for the PE/T-PE nodes to indicate the preferred PW to use
>     for forwarding PW packets to one another, a new status bit is needed
>     to indicate a preferential forwarding status of Active or Standby for
>     each PW in a redundant set.
>
>     In addition, a second status bit is defined to allow peer PE nodes to
>     coordinate a switchover operation of the PW.
>
>
>
>
>
>
> The file can be obtained via
> http://datatracker.ietf.org/doc/draft-ietf-pwe3-redundancy-bit/
>
> IESG discussion can be tracked via
> http://datatracker.ietf.org/doc/draft-ietf-pwe3-redundancy-bit/ballot/
>
>
> No IPR declarations have been submitted directly on this I-D.
>
>
> _______________________________________________
> IETF-Announce mailing list
> IETF-Announce@xxxxxxxx
> https://www.ietf.org/mailman/listinfo/ietf-announce
>


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